Fluoropolymer compositions

ABSTRACT

Compositions comprising a fluoropolymer having interpolymerized units derived from a nitrogen-containing cure site monomer and a catalyst composition are provided. The catalyst composition includes a compound having the general formula:
 
{RA} (−) {QR′ k } (+) 
 
or the precursors thereof, wherein R is a nonfluorinated, partially fluorinated, or perfluorinated alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl or aralkyl, A is an acid- or acid-derivative anion, Q is phosphorous, sulfur, nitrogen, arsenic, or antimony, and each R′ is hydrogen or an alkyl, aryl, aralkyl, or alkenyl group, k is the valence of Q; and optionally (c) an alcohol of the formula R 2 —OH, wherein R 2  is an alkyl group which can be fluorinated.
 
     Also provided are a method of making a fluoropolymer, a method of increasing induction time, and fluoropolymer articles containing curable or cured fluoropolymer compositions.

This application claims priority to pending prior applications U.S. Ser.No. 60/265,498, filed 31, Jan. 2001, U.S. Ser. No. 60/283,464, filed 12,Apr. 2001, and U.S. Ser. No. 60/283,535, filed 12, Apr. 2001. The entiredisclosure of each prior application is considered part of thedisclosure of this application and each is herein incorporated byreference.

TECHNICAL FIELD

This invention relates to curing fluoropolymer compositions havingnitrogen-containing cure-site components and catalyst compositions forcuring such fluoropolymers.

BACKGROUND

Fluorine-containing polymers (also known as “fluoropolymers”) are acommercially useful class of materials. Fluoropolymers include, forexample, crosslinked fluoroelastomers, uncrosslinked fluoroelastomergums, and semi-crystalline fluoroplastics. Fluoroelastomers exhibitsignificant tolerance to high temperatures and harsh chemicalenvironments. Consequently, they are particularly well adapted for useas seals, gaskets, and other molded parts in systems that are exposed toelevated temperatures and/or corrosive chemicals. Such parts are widelyused in the automotive, chemical processing, semiconductor, aerospace,and petroleum industries, among others.

Fluoroelastomers often include a cure-site component to facilitate curein the presence of a catalyst. One class of useful cure-site componentsincludes nitrile group-containing monomers, for which organotincatalysts have been used as curing components. Such catalysts can leaveundesirable extractable metal residues in the cured product and areundesirable for environmental reasons. Ammonia-generating compounds havealso been used as a cure system component. These cure systems lack thedesired level of rheology control during processing.

SUMMARY

In one aspect, the invention relates to a composition that includes (a)a fluoropolymer having interpolymerized units derived from anitrogen-containing cure site monomer; (b) a catalyst composition thatincludes a compound having the general formula:{R(A)_(n)}^((−n)){QR′_(k) ⁽⁺⁾}_(n)  (1)or the precursors thereof added separately or as a mixture;and optionally (c) an alcohol of the general formula R²—OH, wherein R²is an alkyl group having from 1 to 20 carbon atoms, and wherein R² canbe fluorinated.

In another aspect, the invention relates to a composition that includes(a) at least one fluoropolymer having interpolymerized units derivedfrom a nitrogen-containing cure site monomer; (b) one or more otherfluoropolymer(s), which may have nitrogen-containing cure site monomers;(c) a catalyst composition that includes a compound having the generalformula:{R(A)_(n)}^((−n)){QR′_(k) ⁽⁺⁾}_(n)  (1)or in certain cases the precursors thereof added separately or as amixture; (d) a curative targeted to cure the one or more otherfluoropolymer(s); and optionally (e) an alcohol of the general formulaR²—OH, wherein R² is an alkyl group having from 1 to 20 carbon atoms,and wherein R² can be fluorinated.

In Formula (1), R is a C₁-C₂₀ alkyl or alkenyl, C₃-C₂₀ cycloalkyl orcycloalkenyl, or C₆-C₂₀ aryl or alkenyl. R can contain at least oneheteroatom, i.e., a non-carbon atom such as O, P, S, and N, such as anether linkage. R can also be substituted, such as where one or morehydrogen atoms in the group is replaced with F, Cl, Br, or I. Each R canbe perfluorinated, partially fluorinated, or non-fluorinated.

A is an acid anion or an acid derivative anion, e.g., A can be COO, SO₃,SO₂, SO₂NH, PO₃, CH₂OPO₃, (CH₂O)₂PO₂, C₆H₄O, OSO₃, O (in the cases whereR is aryl or alkylaryl),

preferably COO, O, C₆H₄O, SO₃, OSO₃, or

most preferably COO, O, SO₃, and OSO₃; R′ is defined as R (above), and aparticular selection for R′ may be the same or different from the Rattached to A, and one or more A groups may be attached to R;

Q is phosphorous (P), sulfur (S), nitrogen (N), arsenic (As), orantimony (Sb), and k is one greater than the valence of Q.

Each R′ is, independently, hydrogen or a substituted or unsubstitutedalkyl, aryl, aralkyl, or alkenyl group having from 1 to 20 carbon atoms,provided that when Q is nitrogen and the fluoropolymer in thecomposition consists essentially of a terpolymer of TFE, aperfluorovinylether, and a perfluorovinylether cure site monomercomprising a nitrile group not every R′ is H. That is, when thespecified terpolymer is the only fluoropolymer in a composition, thegroup QR′_(k) is not NH₄, however, NR′₄, NHR′₃, NH₂R′₂, and NH₃R′ allfall within the scope of certain embodiments of the present invention.For example, when the cure site monomer is a nitrile-containingpartially-fluorinated vinyl ether, the group QR′_(k) can be NH₄.

Examples of suitable substituents include halogen (e.g., chlorine,fluorine, bromine, iodine), cyano, OR³, and COOR³ groups wherein R³ isselected from hydrogen or the alkali or alkaline earth metals, of whichH, K, Na, and NH₄, are preferred, C₁ to C₂₀ alkyl, aryl, aralkyl,alkenyl, and R (as described above) groups. In addition, any pair ofsaid R′ groups may be connected to each other and the Q atom to form aheterocyclic ring.

In other aspects, the invention provides a method of making afluoropolymer composition involving providing a composition as describedabove, mixing, shaping, curing (i.e., press-curing and optionallypost-curing), and optionally heat aging the composition. The inventionalso provides a method of improving scorch resistance (also calledscorch safety) in a curable fluoropolymer comprising the steps ofproviding a fluoropolymer comprising interpolymerized units derived froma nitrogen-containing cure site monomer and incorporating, into thefluoropolymer, a catalyst composition that includes a compound havingthe general formula: {R(A)_(n)}^((−n)){QR′_(k) ⁽⁺⁾}_(n) or theprecursors thereof added separately or as a mixture, wherein R, A, Q,R′, and k are as defined above in reference to Formula (1). Theinvention also provides articles containing the curable or curedcompositions such as hoses, gaskets, and O-rings.

The compositions retain the advantages of the use of nitrogen-containingcure site monomers (e.g., nitrile group containing cure site monomers)such as the high temperature performance properties typically achievedwhen organotin compounds or ammonia-generating compounds are used as thecatalyst system with such cure site monomers. At the same time, thecompositions exhibit improved properties, such as compression setvalues, as compared to materials made using the organotin compounds.

In addition, the inventive compositions have a controllable cure onsettime (also termed induction time), and cure temperature such thatvarious processing operations such as molding or extrusion are possiblewithout the usual concern for premature curing (scorch). Thus, theinvention provides better scorch resistance than is available with knownammonia-generating cure systems, e.g., those described in WO 00/09569and WO 00/09603. These advantages are achieved while the post-curedcompositions of the present invention exhibit physical properties atleast as good as comparable fluoropolymer compounds made without theinventive compositions.

The inventive compositions are useful in applications where hightemperature exposure and/or harsh chemical exposure are expected.

The details of one or more embodiments of the invention are set forth inthe description below. Other features, objects, and advantages of theinvention will be apparent from the description and from the claims.

DETAILED DESCRIPTION

The composition of the present invention comprises a fluoropolymer, acatalyst composition of Formula (1), and optionally, an alcohol.

Suitable fluoropolymers include interpolymerized units derived from anitrogen-containing monomer and, preferably, at least two principalmonomers. Examples of suitable candidates for the principal monomerinclude perfluoroolefins (e.g., tetrafluoroethylene (TFE) andhexafluoropropylene (HFP)), chlorotrifluoroethylene (CTFE),perfluorovinyl ethers (e.g., perfluoroalkyl vinyl ethers andperfluoroalkoxy vinyl ethers), and optionally, hydrogen-containingmonomers such as olefins (e.g., ethylene, propylene, and the like), andvinylidene fluoride (VDF). Such fluoropolymers include, for example,fluoroelastomer gums and semi-crystalline fluoroplastics.

When the fluoropolymer is perhalogenated, preferably perfluorinated, itcontains at least 50 mole percent (mol %) of its interpolymerized unitsderived from TFE and/or CTFE, optionally including HFP. The balance ofthe interpolymerized units of the fluoropolymer (10 to 50 mol %) is madeup of one or more perfluoro vinyl ethers and a nitrogen-containing curesite monomer (e.g. a nitrile-containing vinylether or an imidatecontaining vinylether). The cure site monomer makes up from about 0.1 toabout 5 mol % (more preferably from about 0.3 to about 2 mol %) of theelastomer.

When the fluoropolymer is not perfluorinated, it contains from about 5to about 90 mol % of its interpolymerized units derived from TFE, CTFE,and/or HFP, from about 5 to about 90 mol % of its interpolymerized unitsderived from VDF, ethylene, and/or propylene, up to about 40 mol % ofits interpolymerized units derived from a vinyl ether, and from about0.1 to about 5 mol % (more preferably from about 0.3 to about 2 mol %)of a nitrogen-containing cure site monomer.

Suitable perfluorinated vinyl ethers include those of the formula:CF₂═CFO(R² _(f)O)_(a)(R³ _(f)O)_(b)R⁴ _(f)  (2)where R² _(f) and R³ _(f) are the same or are different linear orbranched perfluoroalkylene groups of 1-6 carbon atoms; a and b are,independently, 0 or an integer from 1 to 10; and R⁴ _(f) is aperfluoroalkyl group of 1-6 carbon atoms.

A preferred class of perfluoroalkyl vinyl ethers includes compositionsof the formula:CF₂═CFO(CF₂CFXO)_(d)R⁴ _(f)  (3)wherein X is F or CF₃; d is 0-5, and R⁴ _(f) is a perfluoroalkyl groupof 1-6 carbon atoms.

Most preferred perfluoroalkyl vinyl ethers are those where, in referenceto either Formula (2) or (3) above, d is 0 or 1 and each R² _(f), R³_(f), and R⁴ _(f) contains 1-3 carbon atoms. Examples of suchperfluorinated ethers include perfluoromethyl vinyl ether,perfluoroethyl vinyl ether, and perfluoropropyl vinyl ether.

Other useful perfluorinated monomers include those compounds of theformula:CF₂═CFO[(CF₂)_(e)(CFZ)_(g)O]_(h)R⁴ _(f)  (4)where R⁴ _(f) is a perfluoroalkyl group having 1-6 carbon atoms, e is1-5, g is 0-5, h is 0-5 and Z is F or CF₃. Preferred members of thisclass are those in which R⁴ _(f) is C₃F₇, e is 1 or 2, g is 0 or 1, andh is 1.

Additional perfluoroalkyl vinyl ether monomers useful in the inventioninclude those of the formula:CF₂═CFO[(CF₂CF(CF₃)O)_(k)(CF₂)_(p)O(CF₂)_(q)]C_(r)F_(2r+1)  (5)where k is 0-10, p is 1-6, q is 0-3, and r is 1-5. Preferred members ofthis class include compounds where k is 0 or 1, p is 1-5, q is O or 1,and r is 1.

Perfluoroalkoxy vinyl ethers useful in the invention include those ofthe formula:CF₂═CFO(CF₂)_(t)[CF(CF₃)]_(u)O(CF₂O)_(w)C_(x)F_(2x+1)  (6)wherein t is 1-3, u is 0-1, w is 0-3, and x is 1-5, preferably 1.Specific, representative, exemples of useful perfluoroalkoxy vinylethers include CF₂═CFOCF₂OCF₂CF₂CF₃, CF₂═CFOCF₂OCF₃, CF₂═CFO(CF₂)₃OCF₃,and CF₂═CFOCF₂CF₂OCF₃. Mixtures of perfluoroalkyl vinyl ethers andperfluoroalkoxy vinyl ethers may also be employed.

Perfluoroolefins useful in the invention include those of the formula:CF₂═CF—R⁵ _(f),  (7)where R⁵ _(f) is fluorine or a perfluoroalkyl of 1 to 8, preferably 1 to3, carbon atoms.

In addition, partially-fluorinated monomers or hydrogen-containingmonomers such as olefins (e.g., ethylene, propylene, and the like), andvinylidene fluoride can be used in the fluoropolymer of the invention,when the fluoropolymer is not perfluorinated.

One example of a useful fluoropolymer is composed of principal monomerunits of tetrafluoroethylene and at least one perfluoroalkyl vinylether. In such copolymers, the copolymerized perfluorinated ether unitsconstitute from about 10 to about 50 mol % (more preferably 15 to 35 mol%) of total monomer units present in the polymer.

One or more other fluoropolymers may be incorporated into thefluoropolymer having interpolymerized units derived from anitrogen-containing cure site monomer. In addition, one or more otherfluoropolymers (which may include one or more copolymers) may be blendedwith the fluoropolymer (which may comprise a copolymer) havinginterpolymerized units derived from a nitrogen-containing cure sitemonomer. Such other fluoropolymers useful in a blend and/or copolymerinclude the entire array described above, and including homopolymers andcopolymers comprising the interpolymerized units mentioned above. Forexample, polytetrafluoroethylene (PTFE) and PFA(tetrafluoroethylene-perfluorovinylether) are useful. The otherfluoropolymer(s) may lack interpolymerized units derived from anitrogen-containing cure site monomer and/or may include reactive sitesadapted to a selected curative system. For example, two differentfluoropolymers, each having interpolymerized units derived from anitrogen-containing cure site monomer, such as a monomer comprising anitrile group, may be blended to provide the fluoropolymer for thepresent invention.

Another fluoropolymer may be included along with another curative, suchas described below, to provide particular properties. For example, afluoropolymer suitable for peroxide curing and a peroxide curative maybe included to improve chemical stability. Such a blend balances thethermal stability and the chemical stability of the resultant blend, andalso may provide economic benefits. These other curatives also may beused to cure a blend of fluoropolymers having nitrogen-containing curesite monomers without the need to include a fluoropolymer lacking anitrogen-containing cure site monomer.

The fluoropolymer(s) having nitrogen-containing cure site monomerspreferably make up enough of the total fluoropolymer to provideincreased thermal stability over a comparative fluoropolymer that lacksthe composition of the present invention. This amount is generally atleast 25 weight percent (wt %), more preferably at least 50 wt %, of thetotal fluoropolymer in the invention. In some embodiments, thefluoropolymer is comprised entirely of nitrogen-containinginterpolymerized units.

The fluoropolymers may be prepared by methods known in the art. Forexample, the polymerization process can be carried out by free-radicalpolymerization of the monomers as an aqueous emulsion polymerization oras a solution polymerization in an organic solvent. When fluoropolymerblends are desired, a preferable route of incorporation is throughblending the fluoropolymer latices in the selected ratio, followed bycoagulation and drying.

The nature and the amount of end groups are not critical to the successin curing the fluoroelastomers of the invention. For example, thepolymer can contain SO₃ ⁽⁻⁾ end groups generated by an APS/sulfitesystem, or the polymer may contain COO⁽⁻⁾ end groups generated by an APSinitiator system or the fluoroelastomer can have “neutral” end groups,e.g., those generated by the use of fluorosulfinate initiator systems ororganic peroxides. Chain transfer agents of any kind can significantlyreduce the number of end groups. If desired, such as for improvedprocessing, the presence of strong polar end groups such as SO₃ ⁽⁻⁾ canbe minimized and in the case of COO⁽⁻⁾ end groups, the amount can bereduced through post treatments (e.g., decarboxylation).

The cure site component allows one to cure the fluoropolymer. The curesite component can be partially or fully fluorinated. At least one curesite component of at least one fluoropolymer comprises anitrogen-containing group. Examples of nitrogen-containing groups usefulin the cure site monomers of the present invention include nitrile,imidate, amidine, amide, imide, and amine-oxide groups. Usefulnitrogen-containing cure site monomers include nitrile-containingfluorinated olefins and nitrile-containing fluorinated vinyl ethers,such as depicted below:CF₂═CFO(CF₂)_(L)CN  (8)CF₂═CFO[CF₂CF(CF₃)O]_(q)(CF₂O)_(y)CF(CF₃)CN  (9)CF₂═CF[OCF₂CF(CF₃)]_(r)O(CF₂)_(t)CN  (10)CF₂═CFO(CF₂)_(u)OCF(CF₃)CN  (11)where, in reference to the above formulas, L=2-12; q=0-4; r=1-2; y=0-6;t=1-4; and u=2-6. Representative examples of such monomers includeCF₂═CFO(CF₂)₃OCF(CF₃)CN, perfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene),and CF₂═CFO(CF₂)₅CN.

Another suitable cure site component useful in the present invention isa fluoropolymer or fluorinated monomer material containing a halogenthat is capable of participation in a peroxide cure reaction. Such ahalogen may be present along a fluoropolymer chain and/or in a terminalposition. Typically the halogen is bromine or iodine. Copolymerizationis preferred to introduce the halogen in a position along afluoropolymer chain. In this route, a selection of the fluoropolymercomponents mentioned above are combined with a suitable fluorinated curesite monomer. Such a monomer can be selected, for example, from thegeneral formula Z-R_(f)—O_(x)—CF═CF₂, wherein Z is Br or I, R_(f) is asubstituted or unsubstituted C₁-C₁₂ fluoroalkylene, which may beperfluorinated and may contain one or more ether oxygen atoms, and x is0 or 1. When x is 0, examples of the bromo- or iodo-fluorolefinsinclude: bromodifluoroethylene, bromotrifluoroethylene,iodotrifluoroethylene, 1-bromo-2,2-difluoroethylene, and4-bromo-3,3,4,4-tetrafluorobutene-1, and the like. When x is 1, examplesof the bromo- or iodo-fluorovinyl ethers include: BrCF₂OCF═CF₂,BrCF₂CF₂OCF═CF₂, BrCF₂CF₂CF₂OCF═CF₂, CF₃CF(Br)CF₂OCF═CF₂, and the like.In addition, non-fluorinated bromo- or iodo-olefins, e.g., vinyl bromideand 4-bromo-1-butene, can be used.

The amount of cure site component in a side chain position of thefluoropolymer is generally from about 0.05 to about 5 mol % (morepreferably from 0.1 to 2 mol %).

The cure site component may also occur in the terminal position of afluoropolymer chain. Chain transfer agents or initiators are used tointroduce the halogen in a terminal position. Generally, a suitablechain transfer agent is introduced in the reaction medium during polymerpreparation, or derived from a suitable initiator.

Examples of useful chain transfer agents include those having theformula R_(f)Z_(x) wherein R_(f) is a substituted or unsubstitutedC₁-C₁₂ fluoroalkyl radical, which may be perfluorinated, Z is Br or I,and x is 1 or 2. Specific examples involving bromide include: CF₂Br₂,Br(CF₂)₂Br, Br(CF₂)₄Br, CF₂(Cl)Br, CF₃CF(Br)CF₂Br, and the like.

Examples of useful initiators include NaO₂S(CF₂)_(n)X, wherein X is Bror I, and n is 1 to 10.

The amount of cure site component in a terminal position in thefluoropolymer is generally from about 0.05 to about 5 mol % (morepreferably from 0.1 to 2 mol %).

Cure site component combinations are also useful. For example, afluoropolymer containing a halogen that is capable of participation in aperoxide cure reaction may also contain a nitrogen-containing cure sitecomponent such as a nitrile group-containing cure site component.Generally, from about 0.1 to about 5 mol % (more preferably from about0.3 to about 2 mol %) of the total cure site component is incorporatedinto the fluoropolymer.

The fluoropolymer compositions of the present invention are cured, atleast in part, using an organo-onium catalyst composition that is thereaction product of an organo-onium (such as a halide, hydroxide,alkoxide, etc.) and an acid or acid salt. The catalyst compositionincludes a compound having the general formula:{RA}⁽⁻⁾{QR′_(k)}⁽⁺⁾wherein R, A, Q, R′, and k are as described above. Preferred anionsinclude those wherein R is selected from alkyl, benzyl, and phenyl, andA is selected from COO, SO₃, and wherein A is O in the cases where R isaryl or alkenyl.

The catalyst composition of the invention can be hydrated or anhydrous.The catalyst can be in the form of a complex with water and/or alcohol.The catalyst can be prepared by any known means. One example forcatalyst preparation involves converting a commercially-availablehydroxide precursor to a benzoate or acetate complex. Another exampleinvolves reacting an onium halide with an acid metal salt in a solvent,filtering the precipitated metal halide, and removing the solvent. Otherroutes will be apparent to the skilled artisan.

More specifically, the RA anion in the catalyst of the present inventionmay be a carboxylate, alkoxide, sulfate, sulfonate, or phenolate. Asused herein, “substituted” means substituted by conventionalsubstituents that do not interfere with the desired product, and “Ph” isphenyl. Suitable anions include the non-perfluorinated anions of thegeneral formula:(R″)_(x)-Ph_(y)-{(CH₂)_(n)-D}_(m) ⁽⁻⁾wherein each R″ is the same or different alkenyl or alkyl of 1 to 10carbon atoms, which maybe substituted or unsubstituted, x is 0 to 5, yis 0 or 1, n is 0 to 10, m is 1 to 5, and D is selected from COO, OSO₃,SO₃, and O (when y is 1), provided that the sum of x and m is 6 or lessand provided that x and y are not both zero.

Useful anion examples include Ph-COO, Ph-O, CH₃—(CH₂)_(p)—O—SO₃ when pis 1 to 10, and carboxylates of the general formula R—COO wherein R isalkenyl, an alkyl of 1 to 10 carbon atoms, e.g., acetate or propionate,or an aryl of 6 to 20 carbon atoms. Multi-carboxylates, multi-sulfates,multi-sulfonates, and combinations thereof are also useful, e.g.,⁽⁻⁾OOC—(CH₂)_(n)—COO⁽⁻⁾ and ⁽⁻⁾OOC—(CH₂)_(n)—OSO₃ ⁽⁻⁾wherein n is 0 to 10, and Ph-((CH₂)_(p)—COO⁽⁻⁾)_(q) wherein p and q areindependently 1 to 4. A preferred species of bifunctional carboxylicacid is oxalic acid. In the case of multi carboxylates, sulfates, andcombinations, the (CH₂)_(n) chain can also be fluorinated orperfluorinated, e.g., OOC—(CF₂)_(n)—COO. The anion, RA, can also be amaterial selected from CF₃CF(CF₃)CH₂O and C_(n)F_(2n+1)CH₂O wherein n is0 to 100 (preferably 0 to 20, and more preferably 0 to 10). In addition,combinations of two or more compounds as described above can be used forRA in Formula 1.

Representative aromatic polyoxy compounds include the non-perfluorinateddi-, tri-, and tetraoxybenzenes, naphthalenes, and anthracenes, andbisphenols of the formula:⁽⁻⁾O_(z)-Ph-G_(y)-Ph-O_(z) ⁽⁻⁾wherein G is a bond or a difunctional aliphatic, cycloaliphatic, oraromatic radical of 1 to 13 carbon atoms, or a thio, oxy, carbonyl,sulfinyl, or sulfonyl radical, G and/or Ph are optionally substitutedwith at least one chlorine or fluorine atom, y is 0 or 1, each z is,independently, 1 or 2, and any aromatic ring of the polyoxy compound isoptionally substituted with at least one atom of chlorine, fluorine, orbromine atom, or carboxyl or an acyl radical (e.g., —COR, where R is Hor a C₁ to C₈ alkyl, aryl or cycloalkyl group) or alkyl radical with,for example, 1 to 8 carbon atoms. In the above bisphenol formula thatthe oxygen groups can be attached in any position (other than numberone) in either ring. Blends of two or more such compounds can also beused. The mono and bis complexes of the formula:R_(x)-Ph-O-QR′_(k)are also useful. A preferred class of these materials includes thebisphenols, such as those having the general formula:⁽⁻⁾O-Ph-C(CX₃)₂-Ph-O⁽⁻⁾, wherein X is H, Cl, or F (e.g., bisphenol AF).When multifunctional acids are used, the mono-, bis-, andmulti-complexes with QR′_(k) can be used.

As is known in the art, an organo-onium is the conjugate acid of a Lewisbase (e.g., phosphine, amine, and sulfide) and can be formed by reactingsaid Lewis base with a suitable alkylating agent (e.g., an alkyl halideor acyl halide) resulting in an expansion of the valence of the electrondonating atom of the Lewis base and a positive charge on theorgano-onium compound. The preferred organo-onium compounds for thepresent invention contain at least one heteroatom, i.e., a non-carbonatom such as P, S, or N, bonded to organic moieties.

One class of quaternary organo-onium compounds particularly useful inthe present invention broadly comprises relatively positive andrelatively negative ions wherein a phosphorus, sulfur, or nitrogengenerally comprises the central atom of the positive ion, and thenegative ion is an alkyl or cycloalkyl acid anion that may benon-fluorinated, partially fluorinated, i.e., at least one hydrogen atomis replaced with fluorine, provided that at least one hydrogen atomremains, or perfluorinated.

Examples of suitable precursor compounds when Q is phosphorous includetetramethylphosphoniums, tributylallylphosphoniums,tributylbenzylphosphoniums, dibutyldiphenylphosphoniums,tetrabutylphosphoniums, tributyl(2-methoxy) propylphosphoniums,triphenylbenzylphosphoniums, and tetraphenylphosphoniums. Thesephosphoniums can be hydroxides, chlorides, bromides, alkoxides,phenoxides, etc. The tetraalkyl phosphonium hydroxides and tetraalkylphosphonium alkoxides are preferred.

Another class of phosphonium compounds include those selected from thegroup consisting of amino-phosphonium, phosphorane (e.g.,triarylphosphorane), and phosphorous containing iminium compounds.

The amino-phosphonium compounds useful in the present invention includethose described in the art, e.g., in U.S. Pat. No. 4,259,463 (Moggi etal.).

The class of phosphonium compounds useful in this invention includephosphorane compounds such as triarylphosphorane compounds; some of thelatter compounds are known and are described in the art, see forexample, U.S. Pat. No. 3,752,787 (de Brunner), which descriptions areherein incorporated by reference. Such phosphorane compounds are firstreacted with an acid to form a salt, which salt is then used as acurative component. Some of the triarylphosphorane compounds useful inthis invention have the general formula:

wherein Ar is aryl, selected for example, from phenyl, substitutedphenyl, e.g., methoxyphenyl, chlorophenyl, tolyl, and other knowngroups, e.g., naphthyl. R³ and R⁴ are selected from the group consistingof (1) separate groups selected individually from (a) hydrogen, methyl,ethyl, propyl, and carbalkoxy (C₁-C₆ alkyl) in the case of R³, and (b)carbalkoxy (C₁-C₆ alkyl) cyano, and —CONH₂ in the case of R⁴; and (2) asingle group which together with the carbon atom to which the singlegroup is attached form a cyclic group selected from the following:

Representative phosphonium compounds include benzyltris(dimethylamino)phosphonium chloride, and bis(benzyldiphenylphosphine)iminium chloride.

Sulfonium compounds useful in this invention have at least one sulfuratom ionically associated with an anion and covalently bonded to threeorganic moieties (R′) by means of carbon-sulfur covalent bonds. Saidorganic moieties can be the same or different. The sulfonium compoundsmay have more than one relatively positive sulfur atom, e.g.,[(C₆H₅)₂S⁺(CH₂)₄S⁺(C₆H₅)₂]2Cl⁻, and two of the carbon-sulfer covelentbonds may be between the carbon atoms of a divalent organic moiety,i.e., the sulfur atom may be a heteroatom in a cyclic structure.

A class of sulfonium compounds useful in the present invention are saltshaving the formula:

wherein R⁵, R⁶, and R⁷ can be the same or different, provided that atleast one of such groups is aromatic, and such groups can be selectedfrom C4-C20 aromatic radicals (e.g., substituted and unsubstitutedphenyl, thienyl, and furanyl) and C1-C20 alkyl radicals. The alkylradicals include substituted alkyl radicals (e.g., substituents such ashalogen, hydroxy, alkoxy, aryl. Z is selected from oxygen;sulfur; >S═O; >C═O; —SO₂—; —NR⁸—; where R⁸is aryl or acyl (such asacetyl, benzoyl, etc.); a carbon-to-carbon bond; and —CR⁹R¹⁰— where R⁹and R¹⁰ are selected from the group consisting of hydrogen, C₁-C₄ alkylradicals, and C₂-C₄ alkenyl radicals.

Preferably, the sulfonium compounds have at least one aryl group for R′.

When Q is nitrogen, the preferred positive ion has the general formulais NR′₄ or HNR′₃, wherein R′ is as described above. Representativequaternary organo-oniums useful as precursor compounds includephenyltrimethylammoniums, tetrapentylammoniums, tetrapropylammoniums,tetrahexylammoniums, tetraheptylammoniums, tetramethylammoniums,tetrabutylammoniums, tributylbenzyl ammoniums, tributylallylammoniums,tetrabenzylammoniums, tetraphenylammoniums, diphenyl diethylaminoammoniums, triphenylbenzylammoniums,8-benzyl-1,8-diazabicyclo[5.4.0]undec-7-eniums,benzyltris(dimethylamino) phosphoniums, and bis(benzyldiphenylphosphine)iminiums. These ammoniums can be hydroxides, chlorides,bromides, alkoxides, phenoxides, etc. Of these positive ions,tetrabutylammonium and tetraphenylammonium are preferred.

When Q is As or Sb, the preferred positive ions includetetraphenylarsonium chloride and tetraphenylstibonium chloride.

Overall, the tetraalkylphosphonium compounds are more preferred for thepositive ion of the catalyst.

Mixtures of organo-onium compounds are also useful in this invention.

The precursors described above are generally commercially available(e.g., from Aldrich Chemicals, Milwaukee, Wis.) or may be prepared byprocedures known in the art.

The acids or salts of hydrocarbons useful in preparing the catalyst ofthe present invention have the general formula RCOOM, RSO₃M, ROSO₃M, orROM. In these formulas, R is as described above with Formula (1), and Mis hydrogen, or an alkali or alkaline earth metal. Representativematerials for R are the carboxylates, sulfates, sulfonates, andphenolates described above.

In addition, blends of two or more catalyst compounds as describedabove, which includes blends of two or more RA groups and/or two or moreQR′_(k) groups, can be used.

The catalyst composition of the present invention can be prepared by anysuitable method. For example, the two components of the active complexused as the catalyst composition in the present invention,{R(A)_(n)}^((−n)){QR′_(k) ⁽⁺⁾}_(n), can be incorporated separately as anacid or a salt, e.g., RAX wherein X is selected from hydrogen or thealkali or alkaline earth metals, of which H, K, Na, and NH₄, arepreferred, and QR′_(k)Z, wherein Z is selected from an anion, which maybe organic or inorganic, preferably Cl, Br, OH, OR³, or SO₄. The twocomponents can be added to the inventive elastomer gum separately or asa mixture. In this method, the active complex is formed in situ duringprocessing, heating, and curing. To avoid contamination and theinclusion of extractables, which is especially important for cleanapplications (e.g. semiconductors), the complexes should be preparedbefore incorporation into the fluoroelastomer composition, and theresulting salts, XZ, should be filtered or washed out before the activecomplex is incorporated into the elastomer gum. Other suitable methods,which are known in the art, also may be used to prepare the catalystcomposition. For example, the two components of the catalyst compositioncan be dissolved into a suitable solvent (e.g., an alcohol) beforeprecipitating and filtering out the resulting salt, XZ. Salt formationcan be avoided by reacting the onium component as the onium-hydroxide oronium-alkoxide with the acid component of the catalyst composition(e.g., reacting Bu₄NOH with RCOOH). The active complexes can beincorporated into the elastomer gum when dissolved in a solvent or as adried compound. An excess of the QR′_(k) material (e.g., tetraalkylphosphonium chloride) or the free acid (e.g., RAH) does notdetrimentally affect the properties of the polymer.

An effective amount of the selected curative compound{R(A)_(n)}^((−n)){QR′_(k) ⁽⁺⁾}_(n)) is used to crosslink thefluoropolymer. When the amount of curative is too low, the fluoropolymermay not crosslink sufficiently to develop the desired physicalproperties and/or may crosslink more slowly than desired. When theamount of curative is too high, the fluoropolymer may crosslink into amaterial that is less compliant than desired and/or may crosslink toorapidly for the desired process conditions. The selection of aparticular composition can affect the amount of curative desired. Forexample, the type and/or amount of filler selected may retard oraccelerate curing relative to a similar, but unfilled, composition,requiring an appropriate adjustment in the amount of curative that isknown to those skilled in the art.

The composition of the fluoropolymer also affects the amount of one ormore curatives. For example, when a blend of a nitrile containingfluoropolymer and another fluoropolymer lacking nitrile cure sites isused, an effective amount of a first selected curative compound is usedto crosslink the fluoropolymer having interpolymerized units derivedfrom a nitrile group-containing monomer together with an effectiveamount of a second selected curative compound used to crosslink theother fluoropolymer. The first and second selected curatives may havethe same or different composition. That is, either one or both selectedcuratives may function to crosslink either one or both fluoropolymers.

Generally, the effective amount of curative, which may include more thanone composition, is in the range of 0.2 to 10 millimoles curative perhundred parts of gum (mmhr) (more preferably 0.5 to 5 mmhr).

One of the advantages of the present invention is controllable curerheology. After an initial drop in torque, corresponding to an increasein temperature of the material, the inventive compositions haveavailable a relatively long period of time (“induction time”) afterwhich the torque increases rapidly to its final or maximum value. Therapid increase in the torque corresponds to a rapid increase in theviscosity of the composition as it crosslinks. The induction time iscontrollable from seconds to several minutes. This allows a sufficientamount of induction time for a particular inventive composition to beformed or molded before the onset of cure. This rheology also provides arapid completion of the cure cycle after the cure onset, so the curecycle is not unnecessarily prolonged. Thus, compositions of the presentinvention can be completely formed or molded rapidly, cured to a statethat they can be handled without damage, and removed from the mold.

The fluoropolymer composition curing can also be modified by using othertypes of curatives along with the catalyst of the present invention.Examples of such curatives are known and include bis-aminophenols (e.g.,as described in U.S. Pat. Nos. 5,767,204 and 5,700,879), bis-amidooximes(e.g., as described in U.S. Pat. No. 5,621,145), and ammonium salts(e.g., as described in U.S. Pat. No. 5,565,512). In addition,organometallic compounds of arsenic, antimony and tin can be used, e.g.,as described in U.S. Pat. Nos. 4,281,092, and 5,554,680. Particularexamples include allyl-, propargyl-, triphenyl-allenyl-, andtetraphenyltin and triphenyltin hydroxide.

The fluoroelastomer compositions of the invention can be cured using oneor more ammonia-generating compounds along with the catalysts describedabove. “Ammonia-generating compounds” include compounds that are solidor liquid at ambient conditions but that generate ammonia underconditions of cure. Such compounds include, for example, hexamethylenetetramine (urotropin), dicyandiamide, and metal-containing compounds ofthe formula:A^(w+)(NH₃)_(x)Y^(w−)  (15)wherein A^(w+) is a metal cation such as Cu²⁺, Co²⁺, Co³⁺, Cu⁺, andNi²⁺; w is equal to the valance of the metal cation; Y^(w−) is acounterion, typically a halide, sulfate, nitrate, acetate or the like;and x is an integer from 1 to about 7.

Also useful as ammonia-generating compounds are substituted andunsubstituted triazine derivatives such as those of the formula:

wherein R is a hydrogen or a substituted or unsubstituted alkyl, aryl,or aralkyl group having from 1 to about 20 carbon atoms. Specific usefultriazine derivatives include hexahydro-1,3,5-s-triazine and acetaldehydeammonia trimer.

The fluoroelastomer compositions of the invention, including thenitrogen containing cure site monomer-containing fluoropolymer alone,can be cured using one or more peroxide curatives along with thecatalysts described above. Suitable peroxide curatives generally arethose which generate free radicals at curing temperatures, such as thosedescribed in WO 99/48939, the disclosure of which is herein incorporatedby reference. Dialkyl peroxide and bis(dialkyl peroxide), each of whichdecomposes at a temperature above 50° C., are especially preferred. Inmany cases it is preferred to use a di-tertiarybutyl peroxide having atertiary carbon atom attached to peroxy oxygen atom. Among the mostuseful peroxides of this type are2,5-dimethyl-2,5-di(tertiarybutylperoxy)hexyne-3 and2,5-dimethyl-2,5-di(tertiarybutylperoxy)hexane. Other peroxides can beselected from such compounds as dicutnyl peroxide, dibenzoyl peroxide,tertiarybutyl perbenzoate, a,a′-bis(t-butylperoxy-diisopropylbenzene),and di[1,3-dimethyl-3-(t-butylperoxy)-butyl]carbonate. Generally, about1 to 3 parts of peroxide per 100 parts of perfluoroelastomer is used.

Another curative useful in the present invention has the generalformula:CH₂═CH—R_(f)—CH═CH₂,wherein one or more H atoms may be replaced with halogen atoms, such asF, and R_(f) is a C₁-C₈ linear or branched and at least partiallyfluorinated alkylene, cycloalkylene, or oxyalkylene. Similarly, polymerscontaining pendant groups of CH₂═CHR_(f)— are also useful as curativesin the present invention. Such curatives are described, for example, inU.S. Pat. No. 5,585,449.

The combination of catalyst and curative is generally from about 0.01 toabout 10 mol % (more preferably from about 0.1 to about 5 mol %) of thetotal fluoropolymer amount.

The fluoropolymer compositions can include any of the adjuvants commonlyemployed in curable fluoropolymer formulations. For example, onematerial often blended with a fluoropolymer composition as a part of acurative system is a coagent (sometimes also referred to as aco-curative) composed of a polyunsaturated compound that is capable ofcooperating with the peroxide curative to provide a useful cure. Thesecoagents are particularly useful in combination with a peroxidecurative. The coagent(s) can generally be added in an amount equal tobetween 0.1 and 10 parts coagent per hundred parts fluoropolymer (phr),preferably between 1 and 5 phr. Examples of coagents useful with theorgano-onium compound of the present invention include triallylcyanurate; triallyl isocyanurate; tri(methylallyl) isocyanurate;tris(diallylamine)-s-triazine; triallyl phosphite; N,N-diallylacrylamide; hexaallyl phosphoramide; N,N,N′,N′-tetraalkyltetraphthalamide; N,N,N′,N′-tetraallyl malonamide; trivinylisocyanurate; 2,4,6-trivinyl methyltrisiloxane; andtri(5-norbornene-2methylene)cyanurate. Particularly useful is triallylisocyanurate. Other useful coagents include the bis-olefins disclosed inEP 0 661 304 A1, EP 0 784 064 A1 EP 0 769 521 A1, and U.S. Pat. No.5,585,449.

The optional alcohol has the general formula R²—OH, wherein R² is alkylgroup having from 1 to 20 carbon atoms, more preferably 6 to 12 carbonatoms. R² can be fluorinated, e.g., R_(f)—CH₂—OH or R_(f)—CH₂CH₂—OHwherein R_(f) is a perfluoroalkyl, e.g., C_(n)F_(2n+1) where n is 1 to20, or perfluorocycloalkyl, e.g., C_(m)F_(2m−1) where m is 3 to 20, or aC₁-C₂₀ fluoroalkenyl. R_(f) can also be partially fluorinated. As usedherein, “partially fluorinated” means where one or more F atoms in thealkyl group is replaced with H, Cl, Br, or I, provided at least one Fatom remains. R_(f) can also contain at least one heteroatom, i.e., anon-carbon atom such as O, P, S, or N.

While the addition of alcohol is not required, it may be helpful tomodify the viscosity and cure characteristics of the composition. Thealcohol is selected to be compatible in the overall composition. Thealcohol should also remain in a mixture of fluoropolymer with catalystduring milling operations. The alcohol preferably should evaporateduring subsequent processing at higher temperatures, such as duringpost-cure operations. Examples of presently preferred alcohols includeoctanol and decanol. An effective amount of alcohol is used in thecurative system. This amount is determined by several factors includingthe desired ratio of alcohol to catalyst, the particular alcohol chosen,and the milling temperature. The particular level for a selectedcomposition is normally a matter of routine experimentation. Generally,this amount is in the range of 0.01 to 10 (more preferably 0.5 to 5)parts by weight alcohol per hundred parts by weight fluoropolymer.

Thus, a particular composition of the present invention may include twoor more fluoropolymer(s) (provided that at least one fluoropolymerincludes interpolymerized units derived from a nitrogen-containing curesite monomer), a catalyst composition of Formula (1), a peroxidecurative selected to crosslink one or more than one of thefluoropolymer(s), optionally a coagent such as triallyl isocyanurate,and optionally, an alcohol.

Additives such as carbon black, stabilizers, plasticizers, lubricants,fillers, and processing aids typically utilized in fluoropolymercompounding can be incorporated into the compositions, provided thatthey have adequate stability for the intended service conditions. Inparticular, low temperature performance can be enhanced by incorporationof perfluoropolyethers. See, e.g., U.S. Pat No. 5,268,405.

Carbon black fillers are typically also employed in fluoropolymers as ameans to balance modulus, tensile strength, elongation, hardness,abrasion resistance, conductivity, and processability of thecompositions. Suitable examples include MT blacks (medium thermal black)designated N-991, N-990, N-908, and N-907; FEF N-550; and large particlesize furnace blacks. When large size particle black is used, 1 to 70parts filler per hundred parts fluoropolymer (phr) is generallysufficient.

Fluoropolymer fillers may also be present in the compositions.Generally, from 1 to 50 phr of fluoropolymer filler is used. Thefluoropolymer filler can be finely divided and easily dispersed as asolid at the highest temperature used in fabrication and curing of theinventive composition. By solid, it is meant that the filler material,if partially crystalline, will have a crystalline melting temperatureabove the processing temperature(s) of the curable composition(s). Thepreferred way to incorporate fluoropolymer filler is by blendinglatices. This procedure, including various kinds of fluoropolymerfiller, is described in U.S. Ser. No. 09/495,600, filed 01 Feb. 2000,the disclosure of which is herein incorporated by reference.

One or more acid acceptors can also be added to the formulations.However, where the presence of extractable metallic compounds isundesirable (such as for semiconductor applications) the use ofinorganic acid acceptors should be minimized, and preferably avoidedaltogether. Commonly used acid acceptors include, for example, zincoxide, calcium hydroxide, calcium carbonate, magnesium oxide, silicondioxide (silica), etc. These compounds generally are used in thefluoropolymer formulation to bind any HF or other acids that might begenerated at the high temperatures such as may be encountered duringcuring steps or at the temperatures where the fluoropolymers areintended to function.

The curable fluoropolymer compositions of the invention may also becombined with other curable fluoropolymer compositions such asperoxide-curable fluoropolymer compositions. These additional curablefluoropolymer compositions may also employ small amounts of cure sitemonomers as a comonomer. Suitable cure site monomers are those which,when combined with a curative (e.g., a peroxide) and, preferably acoagent, will provide a cured composition. Preferably these cure sitemonomers include at least one halo group (e.g., a bromo or an iodogroup).

The curable fluoropolymer compositions can be prepared by mixing one ormore fluoropolymer(s), the catalyst, any selected additive or additives,any additional curatives (if desired), and any other adjuvants (ifdesired) in conventional rubber processing equipment. The desiredamounts of compounding ingredients and other conventional adjuvants oringredients can be added to the unvulcanized fluorocarbon gum stock andintimately admixed or compounded therewith by employing any of the usualrubber mixing devices such as internal mixers, (e.g., Banbury mixers),roll mills, or any other convenient mixing device. The temperature ofthe mixture during the mixing process typically should not rise aboveabout 120° C. During mixing, it is preferable to distribute thecomponents and adjuvants uniformly throughout the gum for effectivecure.

The mixture is then processed and shaped, such as by extrusion (e.g.,into the shape of a tube or a hose lining) or by molding (e.g., in theform of an O-ring seal). The shaped article can then be heated to curethe gum composition and form a cured article.

Molding or press curing of the compounded mixture usually is conductedat a temperature sufficient to cure the mixture in a desired timeduration under a suitable pressure. Generally, this is between about 95°C. and about 230° C., preferably between about 150° C. and about 205°C., for a period of from about 1 minute to 15 hours, typically from 5minutes to 30 minutes. A pressure of between about 700 kPa and about21,000 kPa is usually imposed on the compounded mixture in a mold. Themolds first may be coated with a release agent and prebaked.

The cure rheology of the compositions of the present invention maintainnear their minimum viscosities during typical processing operations,providing improved scorch resistance and greater options in processingconditions over known materials. Significantly, the advantages inprocessing do not detrimentally affect the resulting physical propertiesof the final cured product and the resultant fluoropolymers of thepresent invention have excellent high-temperature properties and lowcompression set values.

The molded mixture or press-cured article is then usually post-cured(e.g., in an oven) at a temperature and for a time sufficient tocomplete the curing, usually between about 150° C. and about 300° C.,typically at about 232° C., for a period of from about 2 hours to 50hours or more, generally increasing with the cross-sectional thicknessof the article. For thick sections, the temperature during the post cureis usually raised gradually from the lower limit of the range to thedesired maximum temperature. The maximum temperature used is preferablyabout 300° C., and this value is held for about 4 hours or more. Thispost-cure step generally completes the cross-linking and may alsorelease residual volatiles from the cured compositions. One example of asuitable post-cure cycle involves exposing molded parts to heat undernitrogen using six stages of conditions. First, the temperature isincreased from 25 to 200° C. over six hours, then the parts are held at200° C. for 16 hours, after which the temperature is increased from 200to 250° C. over 2 hours. Then the parts are held at 250° C. for 8 hours,after which the temperature is increased from 250 to 300° C. over 2hours. Then the parts are held at 300° C. for 16 hours. Finally, theparts are returned to ambient temperature such as by shutting off theoven heat.

The fluoropolymer compositions are useful in production of articles suchas O-rings, gaskets, tubing, and seals. Such articles are produced bymolding a compounded formulation of the fluoropolymer composition withvarious additives under pressure, curing the article, and thensubjecting it to a post-cure cycle. The curable compositions formulatedwithout inorganic acid acceptors are particularly well suited forapplications such as seals and gaskets for manufacturing semiconductordevices, and in seals for high temperature automotive uses.

The invention will now be described further by way of the followingexamples.

EXAMPLES

The indicated results were obtained using the following test methods,unless otherwise noted. The test results appear in the tables below.

Cure Rheology: Tests were run on uncured, compounded samples using aMonsanto Moving Die Rheometer (MDR) Model 2000 in accordance with ASTM D5289-93a at 177° C., no pre-heat, 30 minute elapsed time, and a 0.5degree arc. Both the minimum torque (M_(L)) and highest torque attainedduring a specified period of time when no plateau or maximum torque wasobtained (M_(H)) were measured. Also measured were the time for thetorque to increase 2 units above M_(L) (“t_(s)2”), the time for thetorque to reach a value equal to M_(L)+0.5(M_(H)−M_(L)) (“t′50”), andthe time for the torque to reach M_(L)+0.9(M_(H)−M_(L)) (“t′90”).

Mooney Scorch: Measurements were taken at 121° C., following theprocedures described in ASTM D 1646. Minimum viscosity (units), and thetime in minutes to increase to various viscosity levels were recorded.For example, the time to reach a 3, 12, and 18 unit rise typically wasrecorded.

Press-Cure: Sample sheets measuring 150×150×2.0 mm were prepared forphysical property determination by pressing at about 6.9 Mega Pascal(MPa) for 30 minutes at 177° C., unless otherwise noted.

Post-Cure: Press-cured sample sheets were exposed to heat under nitrogenusing the following six stages of conditions: 25 to 200° C. over 6hours; 200° C. for 16 hours; 200 to 250° C. over 2 hours; 250° C. for 8hours; 250 to 300° C. over 2 hours; and 300° C. for 16 hours. Thesamples were returned to ambient temperature before testing.

Heat Aging: Press-cured and post-cured sample sheets were exposed toheat in air for 70 hours at 290° C. and then returned to ambienttemperature before testing.

Physical Properties: Tensile Strength at Break, Elongation at Break, andModulus at 100% Elongation were determined using ASTM D 412-92 onsamples cut from the press-cure or post-cure sheet with ASTM Die D.Units are reported MPa.

Hardness: Samples were measured using ASTM D 2240-85 Method A with aType A-2 Shore Durometer. Units are reported in points on the Shore Ascale.

Compression Set: O-ring samples were measured using ASTM 395-89 MethodB. The O-rings had a cross-sectional thickness of 0.139 in. (3.5 mm.).Results are reported as a percentage of the original deflection.

All materials were commercially available from Aldrich Chemical Co.,Milwaukee, Wis. unless otherwise indicated.

Catalyst Preparation: A mixture of 98.66 g of a 40 weight percent (wt %)solution in water of tetrabutyl phosphonium hydroxide (0.143 mol)(Aldrich) was neutralized in a 500 mL flask with 8.6 g of acetic acid(99.7% purity). The mixture was swirled for about 5 minutes (pH paperindicated a pH of 9). Water was removed from the mixture using a rotaryevaporator (rotavap) using a bath temp of around 50° C. until no morewater condensed. Ethanol (100 mL) was added to the flask and thesolution was stripped on the rotavap until no more condensationoccurred. Another 100 mL of ethanol was added to the solution, followingby stripping on the rotovap until no more condensation occurred. Thisyielded 59.95 g of a clear, slightly viscous oil. NMR analysis revealedthat this oil contained 19% ethanol. Karl-Fisher titration revealed thatthis oil contained 1.8 wt % water, along with the desired tetrabutylphosphonium acetate.

A mixture of 62.45 g of a 40 wt % solution in water of tetrabutylphosphonium hydroxide (0.0904 mol) (Aldrich) was placed into a 500 mLround bottom flask. Benzoic acid (11.0 g; 0.0904 mol) was added as asolid and dissolved via swirling the flask. Any chunks of benzoic acidwere broken up with a spatula and all the benzoic acid dissolved. Thewater was stripped using a water aspirator vacuum rotavap with a bathtemperature of 50-70° C. When no more water was condensing, the flaskwas removed from the rotavap, and 20 g ethanol was added to the residue.The residue was dissolved and the ethanol was stripped on the samerotavap at the same temperature until no more ethanol condensed. Theethanol addition and stripping was repeated once. This yielded 40.7 g ofa very pale yellow viscous oil that was analyzed to contain a ratio ofvery close to a 1:1:1 adduct of an ethanol:tetrabutylphosphonim:benzoiccomplex.

Example 1

A fluoroelastomer was prepared by emulsion polymerization whichcontained 65.3 mole percent tetrafluoroethylene (mol % TFE), 33.5 mol %perfluoromethyl vinyl ether (PMVE), and 1.2 mol % of a nitrilegroup-containing cure site monomer, CF₂═CFO(CF₂)₅CN. A catalyst wasprepared by reacting equi-molar amounts of a fluorochemical acid,perfluoro octanoic acid, with sodium methoxide in methanol, then addingan equi-molar amount of tributyl-(2-methoxy)-propyl phosphonium chloridein methanol, and decanting the resulting NaCl to reachtributyl-(2-methoxy)-propyl phosphonium perfluoro octanoate, while theremaining methanol was not stripped.

The fluoropolymer (100 g basis) was compounded with: 1.5 mmhr of thecatalyst (dissolved in methanol), and 0.39 g n-octanol.

Cure rheology tests were run on the uncured, compounded sample. Theresults are included in Table 2, below. A sheet of the compoundedadmixture was pressed cured and tested and subsequently post-cured. Thepost-cured samples were tested, then heat aged and tested, and finallytested for compression set. All test results are included in the tablesbelow.

Example 2

The fluoropolymer compound preparation and testing procedures of Example1 were followed with the addition of 1 g of triphenyl benzylphosphoniumchloride (TPBCl) to the fluoropolymer mixture duringcompounding.

Example 3

The fluoropolymer compound preparation and testing procedures of Example1 were followed with the addition of 40 g of BaSO₄ and 5 g of TiO₂ tothe fluoropolymer mixture during compounding.

Example 4

The fluoropolymer compound preparation and testing procedures of Example1 were followed with the addition of 1 g of TPBCl (as in Example 2) and15 g MT N990 carbon black to the fluoropolymer mixture duringcompounding.

Example 5

The fluoropolymer compound preparation and testing procedures of Example1 were followed while the catalyst level was increased to 3 mmhr, theoctanol level was increased to 0.78 g, and 15 g FEF N550 carbon blackwas added the fluoropolymer mixture during compounding.

Example 6

The fluoropolymer compound preparation and testing procedures of Example5 were followed with the addition of 1 g of TPBCl (as in Example 2) tothe fluoropolymer mixture during compounding.

These results show the high efficiency of the inventive catalyst systemand the excellent physical properties of the inventive fluoropolymercompositions.

Examples 7-8

A fluoroelastomer was prepared by emulsion polymerization whichcontained 66.6 mole % TFE, 32.6 mol % PMVE, and 0.8 mol % of a nitrilegroup-containing cure site monomer, CF₂═CFO(CF₂)₅CN. A catalyst wasprepared by reacting equi-molar amounts of a fluorochemical acid,perfluoro butanoic acid, with sodium methoxide in methanol, then addingan equi-molar amount of tributyl-(2-methoxy)-propyl phosphonium chloridein methanol, and decanting the resulting NaCl to reachtributyl-(2-methoxy)-propyl phosphonium perfluoro butyrate, while theremaining methanol was not stripped.

The fluoropolymer (100 g basis) was compounded with: 2.0 mmhr of thecatalyst (dissolved in methanol), and 0.39 g n-octanol.

Example 7 further included 25 g of FEF N550 carbon black. Example 8further included 40 g BaSO₄ and 5 g TiO₂, but no carbon black.

Cure rheology tests were run on the uncured, compounded samples. A sheetof each compounded admixture was pressed cured and tested andsubsequently post-cured. The post-cured samples were tested, then heataged and tested, and finally tested for compression set.

Examples 9-10

A fluoroelastomer was prepared as in Examples 7 and 8. A catalyst wasprepared by reacting equi-molar amounts of a fluorochemical acid,perfluoro butanoic acid, with sodium methoxide in methanol, then addingan equi-molar amount of triphenylbenzyl phosphonium chloride inmethanol, and decanting the resulting NaCl to reach triphenylbenzylphosphonium perfluoro butyrate, while the remaining methanol was notstripped.

The fluoropolymer (100 g basis) was compounded with: 2.0 mmhr of thecatalyst (dissolved in methanol), and 0.39 g n-octanol.

Example 9 further included 25 g of FEF N550 carbon black. Example 10further included 40 g BaSO₄ and 5 g TiO₂, but no carbon black.

Cure rheology tests were run on the uncured, compounded samples. A sheetof each compounded admixture was pressed cured and tested andsubsequently post-cured. The post-cured samples were tested, then heataged and tested, and finally tested for compression set.

Example 11

A fluoroelastomer was prepared by emulsion polymerization whichcontained 66.6 mole % TFE, 32.6 mol % PMVE, and 0.8 mol % of a nitrilegroup-containing cure site monomer, CF₂═CFO(CF₂)₅CN. A catalyst wasprepared by reacting equi-molar amounts of a fluorochemical acid,perfluoro propanoic acid, with sodium methoxide in methanol, then addingan equi-molar amount of tributyl-(2-methoxy)-propyl phosphonium chloridein methanol, and decanting the resulting NaCl to reachtributyl-(2-methoxy)-propyl phosphonium perfluoro propanoate, while theremaining methanol was not stripped.

The fluoropolymer was compounded with a fluoropolymer filler, PFA 6502N,commercially available from Dyneon, LLC, St. Paul, Minn. using 100 gfluoropolymer to 25 g filler (125 g total fluoropolymer and filler) inaddition to 1.03 mmol of the catalyst (dissolved in methanol), and 0.38g n-octanol.

Cure rheology and Mooney scorch tests were run on the uncured,compounded, filled fluoropolymer sample. A sheet of the compoundedadmixture was pressed cured and tested and subsequently post-cured. Thepost-cured samples were tested, then heat aged and tested, and finallytested for compression set.

Example 12

A fluoroelastomer was prepared as in Example 1. A catalyst-complexsolution was prepared by mixing 0.43 g perfluoro butanoic acid, 0.43 gsodium methoxide in methanol (at 25 weight percent solids), 0.56 gtetrabutyl ammonium chloride in methanol, and 0.40 g n-octanol.

The fluoropolymer (100 g) was compounded with the catalyst-complexsolution and 25 g MT N990 carbon black.

Cure rheology tests were run on the uncured, compounded sample. A sheetof the compounded admixture was pressed cured and tested andsubsequently post-cured. The post-cured samples were tested, then heataged and tested, and finally tested for compression set.

Comparative Example 1 (CE-1)

The fluoropolymer preparation and testing procedures of Example 1 werefollowed except that 1 g hexamethylene tetramine and 15 g FEF N550carbon black was included with 100 g of the fluoropolymer mixture duringcompounding and no inventive catalyst and no alcohol was used.

The physical properties were comparable to the physical properties ofthe fluoropolymer of Example 5, however the inventive material providedimproved scorch resistance.

Comparative Example 2 (CE-2)

A fluoroelastomer was prepared which contained 62.1 mole percenttetrafluoroethylene, 36.8 mole percent perfluoromethyl vinyl ether, and1.1 mole percent of a nitrile group-containing cure site monomer,CF₂═CFO(CF₂)₅CN, by aqueous emulsion polymerization. The resultingpolymer (100 g) was compounded with: 15 g of FEF N550 carbon black and2.0 g of tetraphenyl tin. Cure rheology tests were run on the uncured,compounded sample.

Example 13

A fluoroelastomer and a catalyst were prepared as in Example 1.

The fluoropolymer (100 g basis) was compounded with 2.06 g of thecatalyst (dissolved in methanol), and 15 g FEF N550 carbon black, but non-octanol was added.

Cure rheology and Mooney scorch tests were run on the uncured,compounded sample. The results (included in the tables) show that theExample 13 material had a higher minimum viscosity and a higher maximumviscosity than the Comparative Examples made without the catalyst andfluoropolymer of the invention.

Comparative Examples CE-3, 4, and 5

A fluoroelastomer was prepared as in Example 1. The fluoropolymer (100 gbasis) was compounded with 1.24 g perfluoro octanoic acid and 15 g FEFN550 carbon black. CE-4 further included 0.40 g n-octanol. CE-5 furtherincluded 0.80 g n-octanol.

Cure rheology and Mooney scorch tests were run on the uncured,compounded samples. The results are included in the tables below.

The testing was stopped after one hour during Examples 3, 5, and 11 andafter two hours during Example 13. These results show that the inventivecatalyst system provides excellent scorch resistance, much better thanin the comparative material.

Example 14

A first fluoropolymer gum was prepared by emulsion polymerization whichcontained 62.2 mole percent tetrafluoroethylene (mol % TFE), 36.6 mol %perfluoromethyl vinyl ether (PMVE), and 1.2 mol % of a nitrilegroup-containing cure site monomer, CF₂═CFO(CF₂)₅CN.

A second fluoropolymer gum was prepared by emulsion polymerization whichcontained 62.0 mol % TFE, 37.4 mol % PMVE, and 0.6 mol %bromotrifluoroethylene.

A catalyst was prepared by reacting equi-molar amounts of afluorochemical acid, perfluoro octanoic acid, with sodium methoxide inmethanol, then adding an equi-molar amount oftributyl-(2-methoxy)-propyl phosphonium chloride in methanol, anddecanting the resulting NaCl to reach tributyl-(2-methoxy)-propylphosphonium perfluoro octanoate, while the remaining methanol wasstripped.

A fluoropolymer blend (70 g first fluoropolymer and 30 g secondfluoropolymer basis) was compounded with: 15 grams per hundred grams gum(phr) of FEF N550 carbon black, 1.25 mmhr of the catalyst, 0.8 mmhrperoxide (2,5-dimethyl-2,5-di(t-butyperoxy) hexane, available as Varox®DBPH from R.T. Vanderbilt Co., Norwalk, Conn.), 1.5 gtriallylisocyanurate (TAIC), and 0.4 g n-octanol.

Cure rheology tests were run on the uncured, compounded sample. A sheetof the compounded admixture was pressed cured and tested andsubsequently post-cured. The post-cured samples were tested, then heataged and tested, and finally tested for compression set.

Examples 15 and 16

In Example 15, a fluoroelastomer gum was prepared by emulsionpolymerization which contained 62.2 mole percent tetrafluoroethylene(mol % TFE), 36.6 mol % perfluoromethyl vinyl ether (PMVE), and 1.2 mol% of a nitrile group-containing cure site monomer, CF₂═CFO(CF₂)₅CN. Acatalyst was prepared by reacting 0.55 g benzoic acid, 0.64 g NaOCH₃solution in methanol (25% solids), and 1.0 g tributyl-(2-methoxy)-propylphosphonium chloride in methanol (85% solids), and 12 g methanol. Theresulting NaCl was decanted from the catalyst and the remaining methanolwas stripped. Then 3 millimoles catalyst per hundred grams gum (mmhr) ofthe resulting tributyl-(2-methoxy)-propyl phosphonium benzoate catalystwas compounded with 100 g of the fluoropolymer gum, 0.8 g n-decanol, and15 grams per hundred grams gum (phr) of FEF N550 carbon black.

In Example 16, a fluoropolymer gum was prepared and compounded as aboveexcept that the same quantity (3 mmhr) of a tributyl-(2-methoxy)-propylphosphonium acetate catalyst was substituted. This catalyst was preparedby the method described above except that an equi-molar amount ofglacial acetic acid was substituted for the benzoic acid.

Cure rheology tests were run on the uncured, compounded samples. Sheetsof the compounded admixtures were pressed cured and tested andsubsequently post-cured. The post-cured samples were tested, then heataged and tested, and finally tested for compression set.

Example 17

A fluoropolymer was prepared by emulsion polymerization which contained62.0 mol % TFE, 37.4 mol % PMVE, and 0.6 mol % bromotrifluoroethylene.This fluoropolymer (30 g) was compounded with: 70 g of thefluoroelastomer of Example 15, 1.5 mmhr of the catalyst of Example 1,0.6 mmhr peroxide (2,5-dimethyl-2,5-di(t-butyperoxy) hexane, availableas Varox® DBPH from R.T. Vanderbilt Co., Norwalk, Conn.), 1 gtriallylisocyanurate (TAIC), 15 phr FEF N550 carbon black, and 0.4 gn-octanol.

Cure rheology tests were run on the uncured, compounded sample. A sheetof the compounded admixture was pressed cured and tested andsubsequently post-cured. The post-cured samples were tested, then heataged (70 h at 270° C.) and tested, and finally tested for compressionset. All test results are included in the tables below.

In the following tables, N/M indicates that the property was notmeasured, TS was used for Tensile Strength, Elong. was used forelongation, and Mod. was used for modulus.

TABLE 1 CE 1 and CE 2 Results CE-1 CE-2 M_(L) (N m) 0.156 0.228 M_(H) (Nm) 1.386 1.773 t_(s)2 (min) 1.78 0.48 t'50 (min) 3.72 0.76 t'90 (min)39.28 5.75 After Press Cure and Post Cure: Tensile Strength at Break(MPa) 13.1 13.75 Elongation at Break (%) 95 144 100% Modulus (MPa) —7.39 Shore A Hardness 73 72 Compression Set (%) 70 hrs at 200° C. 15.559.5 Compression Set (%) 70 hrs at 230° C. — 76.6 Compression Set (%) 22hrs at 300° C. — 100 After Heat Aging: Tensile Strength at Break (MPa)11.86 Elongation at Break (%) 250 100% Modulus (MPa) 3.65 Shore AHardness 71

TABLE 2 Test Results Example 1 2 3 4 5 6 7 8 9 10 11 12 14 CureRheology: M_(L) (N m) 0.053 0.037 0.063 0.07 0.064 0.088 0.096 0.0850.146 0.188 0.182 0.113 1.198 M_(H) (N m) 0.473 0.489 1.2 0.603 1.0530.888 0.635 1.078 0.347 0.44 0.833 1.245 0.112 t_(s)2 (min) 12.46 7.795.35 5.39 3.78 1.87 5.93 3.26 n/a 9.63 10.88 8.54 2.28 t'50 12.19 7.796.93 6.41 4.63 2.21 6.16 4.11 3.05 3.71 11.7 9.33 8.14 (min) t'90 20.7621.34 14.32 18.91 13.45 5.68 9.02 7.49 11.87 9.81 19.63 12.15 7.67 (min)After Press-Cure and Post-Cure: TS at 6.56 6.7 11.6 12.14 14.09 16.7814.78 12.58 12.12 11.73 13.51 19.57 9.57 Break (MPa) Elong. at 230 218155 163 108 107 219 232 237 326 229 156 300 Break (%) 100% 1.39 1.426.56 3.77 12 14.93 6.18 5.69 5.17 3.94 4.21 8.25 2.83 Mod. (MPa) Shore A55 55 70 68 77 77 78 71 73 70 72 73 71 Hardness After Heat-Aging: TS at9.38 6.83 9.38 13.58 15.87 14.67 10.34 8.92 8.54 6.91 12.76 13.11 8.23Break (MPa) Elong. at 272 234 210 206 155 120 302 305 345 397 250 181357 Break (%) 100% 1.25 1.29 4.61 2.92 7.6 11.17 3.94 3.41 3.03 2.523.94 5.8 2.22 Mod. (MPa) Shore A 55 55 71 66 74 77 73 70 72 67 70 72 70Hardness Weight 1.4 0.95 1.85 0.8 1.1 1 1 0.9 1.1 1.2 N/M 1.4 0.9 Loss(%)

TABLE 3 Test Results Example: 15 16 17 Cure Rheology M_(L) (N m) 0.09260.0994 0.1333 M_(H) (N m) 0.8361 0.8406 0.9943 t_(s)2 (min) 4.55 2.360.9 t'50 (min) 6.72 3.17 1.39 t'90 (min) 22.11 8.53 5.36 Press Cured andTS at Break (MPa) 16.42 15.73 13.96 Post Cured Elongation at Break (%)114 110 145 100% Modulus (MPa) 12.69 13.11 7.81 Shore A Hardness 75 7474 Heat Aged* TS at Break (MPa) 14.09 14.95 9.86 Elongation at Break (%)150 153 211 100% Modulus (MPa) 7.14 8.12 3.50 Shore A Hardness 73 71 71Weight Loss (%) 1.4 1.1 1.4

Example 17 was heat aged for 70 h at 270° C. rather than the 290° C. ofthe other examples.

TABLE 4 Cure Rheology Example Number: 13 CE-3 CE-4 CE-5 M_(L) (N m)0.099 0.070 0.067 0.050 M_(H) (N m) 1.557 0.107 0.095 0.249 t_(s)2 (min)4.79 — — — t'50 (min) 5.79 33.12 7.89 50.34 t'90 (min) 9.41 55.47 39.0657.91 The designation “—” indicates that no viscosity increase wasobserved.

TABLE 5 Compression Set Example: 1 2 3 4 5 6 7 8 70 hrs at N/M 8.7 10.611.9 10.9 11 15 12.2 200° C. 70 hrs at N/M 14.41 13 13.9 15.6 16.6 1920.4 230° C. 70 hrs at N/M N/M 33.8 26.7 26.5 28.6 N/M N/M 290° C.Example: 9 10 11 12 14 15 16 17 70 hrs at 26.5 21.3 16.3 14.6 50.1 11.610.9 32.8 200° C. 70 hrs at 29.8 25.9 22.5 20.4 62.5 13.4 15.5 59.8 230°C. 70 hrs at N/M N/M 47 39.6 72.5 27.4 28.7 *91.2 290° C. The asteriskon the third compression set test for Example 17 indicates that 70 h at270° C. was used, rather than 290° C.

TABLE 6 Mooney Scorch Exam- ple 3 5 11 13 15 16 CE-1 Min- 53.2 42.2 58.849.5 7.095 5.932 74.1 imum vis- cosity t-3 — — — — >120 >120 5.83 (min)t-10 — — — — >120 >120 9.91 (min) t-18 — — — — >120 >120 13.91 (min)

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.

1. A composition comprising: (a) a fluoropolymer comprisinginterpolymerized units derived from a nitrogen-containing cure sitemonomer; (b) a catalyst composition that includes a compound having thegeneral formula: {R(A)_(n)}^((−n)){QR′_(k) ⁽⁺⁾}_(n) or the precursorsthereof added separately or as a mixture; wherein R is a C₁-C₂₀ alkyl oralkenyl, C₃-C₂₀ cycloalkyl or cycloalkenyl, or C₆-C₂₀ aryl or aralkyl,which may be nonfluorinated, partially fluorinated, or perfluorinated,{R(A)_(n)}^((−n)) is an acid anion or an acid derivative anion, n is thenumber of A groups in the anion, Q is phosphorous, sulfur, nitrogen,arsenic, or antimony, each R′ is, independently, hydrogen or asubstituted or unsubstituted C₁-C₂₀ alkyl, aryl, aralkyl, or alkenylgroup, provided that when Q is nitrogen and the only fluoropolymer inthe composition consists essentially of a terpolymer oftetrafluoroethylene, a perfluorovinylether, and a perfluorovinylethercure site monomer comprising a nitrile group not every R′ is H, and k isone greater than the valence of Q; and optionally (c) an alcohol of thegeneral formula R²—OH, wherein R² is an alkyl group having from 1 to 20carbon atoms, and wherein R² is optionally fluorinated.
 2. A compositionaccording to claim 1 wherein A is selected from the group consisting of:COO, O when R is aryl or alkylaryl, SO₃, SO₂, SO₂NH, PO₃,CF₃CF(CF₃)CH₂O, C_(n)F_(2n+1)CH₂O wherein n is 0 to 100, CH₂OPO₃,(CH₂O)₂PO₂, C₆H₄O, OSO₃,

and

wherein R′ is as defined in claim
 1. 3. A composition according to claim1 wherein a precursor of R(A)_(n) has the general formula selected fromthe group consisting of RCOOM, ROSO₃M, RSO₃M, and ROM, wherein M ishydrogen, or an alkali or alkaline earth metal.
 4. A compositionaccording to claim 1 wherein R(A)_(n) is selected from the formula(R″)_(x)-Ph_(y)-{(CH₂)_(n)-D}_(m) wherein each R″ is the same ordifferent C₁-C₁₀ alkenyl or alkyl, x is 0 to 5, y is 0 or 1, n is 0 to10, m is 1 to 5, and D is selected from COO, OSO₃, SO₃, and O (when y is1), provided that the sum of x and m is 6 or less and provided that xand y are not both zero; RCOO wherein R is alkenyl, an alkyl of 1 to 10carbon atoms, or an aryl of 6 to 20 carbon atoms;⁽⁻⁾OOC—(CX₂)_(t)—COO⁽⁻⁾ wherein t is 0 to 10, X=H, F, or Cl; andPh-((CH₂)_(p)—COO⁽⁻⁾)_(q) wherein p and q are independently 1 to 4;CF₃CF(CF₃)CH₂O or C_(d)F_(2d+1)CH₂O wherein d is 0 to 100; and blends oftwo or more such compounds.
 5. A composition according to claim 1wherein R(A)_(n) is selected from the general formula⁽⁻⁾O_(z)-Ph-G_(y)-Ph-O_(z) ⁽⁻⁾ wherein G is a bond or a difunctionalaliphatic, cycloaliphatic, or C₁-C₁₃ aromatic radical, or a thio, oxy,carbonyl, sulfinyl, or sulfonyl radical, G and/or Ph are optionallysubstituted with at least one Cl or F atom, y is 0 or 1, each z is,independently, 1 or 2, and any aromatic ring of the polyoxy compound isoptionally substituted with at least one atom of Cl, F, or Br atom, orcarboxyl, or an acyl radical, or an alkyl radical; and blends of two ormore such compounds.
 6. A composition according to claim 1 whereinR(A)_(n) is selected from the general formula ⁽⁻⁾O-Ph-C(CX₃)₂-Ph-O⁽⁻⁾,wherein X is H, Cl, or F; and blends of two or more such compounds.
 7. Acomposition according to claim 1 wherein a precursor of QR′_(k) isselected from the group consisting of tetramethylphosphoniums,tributylallylphosphoniums, tributylbenzylphosphoniums,dibutyldiphenylphosphoniums, tetrabutylphosphonium, tributyl(2-methoxy)propylphosphoniums, triphenylbenzylphosphoniums, andtetraphenylphosphoniums.
 8. A composition according to claim 1 wherein aprecursor of QR′_(k) is selected from the group consisting ofphenyltrimethylammoniums, tetrapentylammoniums, tetrapropylammoniums,tetrahexylammoniums, tetraheptylammoniums, tetramethylammoniums,tetrabutylammoniums, tributylbenzyl ammoniums, tributylallylammoniums,tetrabenzylammoniums, tetraphenylammoniums, diphenyl diethylaminoammoniums, triphenylbenzylammoniums,8-benzyl-1,8-diazabicyclo[5.4.0]undec-7-eniums,benzyltris(dimethylamino) phosphoniums, and bis(benzyldiphenylphosphine)iminiums.
 9. A composition of claim 1 wherein the catalystcomposition is prepared in situ.
 10. A composition according to claim 1wherein the catalyst composition is prepared from components dissolvedin a solvent.
 11. A composition according to claim 1 wherein thefluoropolymer comprises interpolymerized units derived from (i)tetrafluoroethylene, and optionally (ii) one or more perfluorovinylethers of the formula: CF₂═CFO(R² _(f)O)_(a) (R³ _(f)O)_(b)R⁴ _(f)wherein R² _(f) and R³ _(f) are the same or are different linear orbranched perfluoroalkylene groups of 1-6 carbon atoms; a and b are,independently, 0 or an integer from 1 to 10; and R⁴ _(f) is aperfluoroalkyl group of 1-6 carbon atoms.
 12. A composition according toclaim 11 wherein the fluoropolymer further comprises interpolymerizedunits derived from monomers selected from the group consisting ofperfluoroolefins, partially-fluorinated olefins, non-flourinatedolefins, vinylidene fluoride, and combinations thereof.
 13. Acomposition according to claim 1 wherein said cure site monomer isselected from a fluorinated olefin and a nitrile-containing monomer. 14.A composition according to claim 1 wherein said cure site monomer is anitrile-containing monomer having the formula CF₂═CFO(CF₂)_(L)CN;CF₂═CFO(CF₂)_(u)OCF(CF₃)CN; CF₂═CFO[CF₂CF(CF₃)O]_(q)(CF₂O)_(y)CF(CF₃)CN;or CF₂═CF[OCF₂CF(CF₃)]_(r)O(CF₂)_(t)CN; wherein L=2-12; q=0-4; r=1-2;y=0-6; t=1-4, and u=2-6; andperfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene).
 15. A compositionaccording to claim 1 further comprising a filler selected fromfluoropolymer filler, carbon black, and combinations thereof.
 16. Thecomposition of claim 1 wherein the fluoropolymer is selected from afluoroelastomer and a fluoroplastic.
 17. The composition of claim 1wherein the composition has an induction time below about 15 minutes ata temperature of about 175° C.
 18. The composition of claim 1 whereinthe composition has a scorch resistance greater than the scorchresistance of a comparative composition tested at the same temperature,which comparative composition has the same fluoropolymer composition ofclaim 1 but with a urotropin curative.
 19. The composition of claim 1further comprising an additional curative material.
 20. The compositionof claim 19 wherein the additional curative material is selected fromammonia-generating compounds, substituted triazine derivatives,unsubstituted triazine derivatives, peroxides, bis-aminophenols,bis-amidooximes, and organotin compounds.
 21. A shaped articlecomprising the fluoropolymer composition of claim
 1. 22. The compositionof claim 1 further comprising a fluoropolymer containinginterpolymerized units derived from monomers selected from the groupconsisting of perfluoroolefins, partially-fluorinated olefins,non-fluorinated olefins, vinylidene fluoride, perfluorovinyl ethers, andcombinations thereof.
 23. The composition according to claim 22comprising a curative that increases MDR torque in the fluoropolymercomposition at 177° C. by at least about 0.01 Nm.
 24. The composition ofclaim 22 further comprising a curative material selected from ammoniumsalts, ammonia-generating compounds, substituted triazine derivatives,unsubstituted triazine derivatives, peroxides, bis-aminophenols,bis-amidooximes, and organotin compounds; and optionally a coagent. 25.The composition of claim 24 wherein the coagent is selected fromtriallyl cyanurate; triallyl isocyanurate; tri(methylallyl)isocyanurate; tris(diallylamine)-s-triazine; triallyl phosphite;N,N-diallyl acrylamide, hexaallyl phosphoramide; N,N,N′,N′-tetraalkyltetraphthalamide; N,N,N′,N′-tetraallyl malonamide; trivinylisocyanurate; 2,4,6-trivinyl methyltrisiloxane; andtri(5-norbornene-2-methylene)cyanurate.
 26. The composition of claim 24wherein the additional fluoropolymer includes interpolymerized unitscontaining a halogen that is capable of participation in a peroxide curereaction and wherein the additional curative is a peroxide, andoptionally further comprising a triallyl cyanurate coagent.
 27. A shapedarticle comprising the fluoropolymer composition of claim
 22. 28. Thecomposition of claim 1 wherein R(A)_(n) is selected from the formula⁽⁻⁾CF₃(CF₂)_(m)COO⁽⁻⁾ wherein n is 1, 2, or 6, and wherein QR′_(k) isselected from tetrabutylphosphonium andtributyl(2-methoxy)propylphosphonium.
 29. The composition of claim 1wherein R(A)_(n) is selected from the formula ⁽⁻⁾OOC(CF₂)_(n)COO⁽⁻⁾wherein p is 2 or 4, and wherein QR′_(k) is selected fromtetrabutylphosphonium and tributyl(2-methoxy)propylphosphonium.
 30. Thecomposition of claim 1 wherein R(A)_(n) is selected from acetate andbenzoate, and wherein QR′_(k) is selected from tetrabutylphosphonium andtributyl(2-methoxy)propylphosphonium.
 31. A method of making afluoropolylmer composition comprising the steps of: a) forming a mixturecomprising a fluoropolymer having interpolymerized units derived from anitrogen-containing cure site monomer, a catalyst composition comprisinga compound having the formula: {R(A)_(n)}^((−n)){QR′_(k) ⁽⁺⁾}_(n) or theprecursors thereof added separately or as a mixture, wherein R is aC₁-C₂₀ alkyl or alkenyl, C₃-C₂₀ cycloalkyl or cycloalkenyl, or C₆-C₂₀aryl or alkylaryl, A is an acid anion or an acid derivative anion group,which may be heterocyclic, Q is P, S, N, As, or Sb, and each R′ is,independently, hydrogen or a substituted or unsubstituted C₁-C₂₀ alkyl,aryl, aralkyl, or alkenyl group, provided that when Q is nitrogen andthe only fluoropolymer in the composition consists essentially of aterpolymer of TFE, a perfluorovinylether and a perfluorovinylether curesite monomer comprising a nitrile group not every R′ is H, and k is onegreater than the valence of Q, and optionally in the presence of analcohol of the general formula R²—OH, wherein R² is a C₆-C₂₀ alkylgroup; b) shaping the mixture; c) curing the shaped mixture; andoptionally d) heat aging the cured mixture.
 32. A method according toclaim 31 wherein the catalyst is added in a form selected from acompound and a mixture of catalyst precursors.
 33. A method according toclaim 31 wherein individual components of the catalyst are separatelyadded to the fluoropolymer composition.
 34. A method according to claim31 wherein the step of curing further comprises press-curing andoptionally post-curing.
 35. A method for increasing the induction periodin a curable fluoropolymer composition comprising the steps of: a)providing a fluoropolymer comprising interpolymerized units derived froma nitrogen-containing cure site monomer; and b) incorporating, into thefluoropolymer, a catalyst composition that includes a compound havingthe general formula: {R(A)_(n)}^((−n)){QR′_(k) ⁽⁺⁾}_(n) or theprecursors thereof added separately or as a mixture, wherein R is aC₁-C₂₀ alkyl or alkenyl, a C₃-C₂₀ cycloalkyl or cycloalkenyl or a C₆-C₂₀aryl or alkylaryl; A is an acid anion or an acid derivative anion; Q isP, S, N, As, or Sb; each R′ is, independently, hydrogen or a substitutedor unsubstituted C₁-C₂₀ alkyl, aryl, aralkyl, or alkenyl group, providedthat when Q is N and the only fluoropolymer in the composition consistsessentially of a terpolymer of TFE, a perfluorovinylether, and aperfluorovinylether cure site monomer comprising a nitrile group notevery R′ is H; and k is one greater than the valence of Q.
 36. Themethod of claim 35 further comprising the step of incorporating analcohol of the general formula R²—OH, wherein R² is a C₁-C₂₀ alkylgroup, and wherein R² can be fluorinated.
 37. The method of claim 35further comprising the step of: c) shaping the composition.
 38. Themethod of claim 37 further comprising the step of: d) curing the shapedcomposition; and optionally e) heat aging the cured composition.
 39. Themethod of claim 38 wherein the step of curing includes press-curing, andoptionally post-curing.